holy day prevents all combat damage, even those dealt by your blockers. this card prevents all damage dealt from target attacking creature, so your 5/5 baneslayer angel can kill a panglacial wurm withought being destroyed or you taking any damage

I'll try holy day if I'm wanting to prevent ALL combat from happening...but if I want some cool combat shenanigans, this gives you a much different effect than Holy Day or Fog...still not altogether that powerful, but surprising none-the-less.

Too often cards like this only buy you time when you've already lost, or waste space in your hand when you could try to win. I like the idea of springing a surprise - but normally when I'm attacked it would take more than this to turn the tide.